The present invention pertains to a medical examination apparatus and method for detecting breast cancer. In particular, the present invention pertains to an examination table having scanning equipment, including microwave equipment and features to aid in screening or diagnosis of breast cancer.
Breast cancer is a major health problem for women. While early detection leads to improved treatment and increased longevity, the existing low-cost screening methods leave much to be desired. For example, as many as 10 to 30% of the malignant tumors in mammogram-screened women go undetected. The result is that about 16,000 women who annually have a mammogram will have a malignant tumor and not know it. Some 20 million women annually fail to comply with the American Cancer Society recommendations for annual mammograms and about 120,000 of these women develop late stage, difficult-to-treat breast cancer. The reasons for the non-compliance are, in part, that mammography is physically uncomfortable, provides uncertain results and poses an ionizing radiation risk. The physical discomfort from mammograms arises because 40% of the tumors occur near the armpit or axilla. Thus, the breast must be compressed between two plates to assure that the tumors near the armpit are imaged. The excess treatment costs for these 120,000 unscreened women are on the order of several billion dollars and the social costs are high in terms of reduced longevity and impaired life style.
A number of novel electromagnetic systems have been investigated that addresses these problems on an analytical and small-scale laboratory basis. However, these have not considered how the patient can be comfortably, safely and reliably examined by physicians on a routine basis to screen women or diagnose women for breast cancer.
Both low-frequency and microwave systems have been or are being considered. These systems detect the high water content of the malignant tumors or lesions that are embedded in the low-water-content normal breast tissues. While some of these systems have been demonstrated theoretically or in small-scale laboratory tests, no provision for large-scale, reliable and comfortable examinations has been noted.
For example, a low-frequency, electrical-impedance measurement system was commercially offered that determined the presence of a malignant tumor. For this, a hand-held sensor with exposed electrodes was physically drawn across the surfaces of the breast. This low-frequency system measured the impedance variations between electrodes that are in physical contact with the surface of the breast. For this, the patient lies on her back and the electrodes are indexed over the surface of the breast. This technique required physically manipulating the breast and this introduced uncertainties as to the location of the electrodes and lead to uncertain results. These uncertain results caused this low-frequency method to be subsequently abandoned.
In another version, the electrodes are all located on a flat plate that is pressed against the breast and may not detect tumors or lesions near the armpit or periphery of the plate. A major difficulty with these low-frequency techniques is that the results require considerable training to correctly diagnose the results of the measurements.
A microwave method applied unfocused 900 megahertz energy directly to the breast via a resonant, open-faced, microwave cavity. The cavity was hand held and was repositioned at different locations over both of the breasts. By comparing the data from one breast with the other, some tumors were found in older women, except for tumors near the nipples. Tumors in younger women were not detected. Beyond these initial tests, no further work was reported.
A concept for a 10 GHz, continuous-wave microwave beam is disclosed in Sepponen U.S. Pat. No. 4,641,659, to scan the breast via a dielectric plate that is pressed against the breast. The beam is developed from an open-ended waveguide antenna that is mechanically scanned across the dielectric plate to form a 2-D image of the backscattered perturbations that might come from a tumor. Sepponen recommends dielectric materials of the scan plate to match the dielectric properties of the normal breast tissue. While some matching is beneficial in Sepponen's case this match must be precise in order to avoid reflections that could mask the desired returns. This is difficult, especially over a wide bandwidth, for both the dielectric constant and the conductivity. However, such values are only commercially available in visually opaque materials (Emerson Cuming). The matching concept alone is impractical because the dielectric properties of the breast vary widely, and these are a function of the patient's age, menses, lactation, and weight. This mismatch will create reflections that mask the desired returns. Sepponen is silent as to how the breast can be comfortably held in a fixed position for the several minutes needed to conduct a scan and does not disclose a support system. Further, means or methods are not described where tumors or lesions near the armpit are detected. Also, Sepponen does not provide a means to record the location of a tumor or lesion relative to the imprint of the breast on the dielectric plate, which may be needed for subsequent treatment of the tumor. Finally, Sepponen does not disclose an orientation system.
Many microwave, infrared and optical systems have been proposed to detect breast tumors that use an examination table with a hole in the table where the breast hangs pendent in a test chamber. Microwave, infrared or optical energy is propagated through the breast and the scattered energy is collected by sensors surrounding the pendent breast. The microwave approach is exempflied by Meany (“A Clinical Prototype For Active Microwave Imaging of the Breast,” P. Meany, M. Fanning, D. Li, S. Poplack, K. Paulsen; IEEE Transactions on Microwave Theory and Techniques, Vol. 48, No. 11, November 2000). Fear (“Microwave Detection of Breast Cancer,” E. C. Fear, M. A. Stuchy; IEEE Transactions on Microwave Theory and Technique, Vo. 48, No. 11, November 2000) has proposed an alternative microwave breast tumor imaging system that beams microwave energy through the breast. Meaney's system employs an iterative technique to develop spatial distribution of the conductivity within the breast. Fear employs imaging techniques similar to those described in patents developed by this applicant, such as in U.S. Pat. No. 5,704,355. To do the scan through the breast, the woman lies face down on an examination table so that her breast hangs pendent in a test chamber that is sometimes filled with water or other liquids. This arrangement also misses tumors near the armpit. A major difficulty with these methods is that the surface of the breast is not well defined with respect to the locations of the antennas that are positioned around the breast. This increases computational complexity and may lead to diagnosis problems.
Wide band, confocal pulsed microwave imaging has been proposed and described in U.S. Pat. Nos. 5,704,355 5,807,257 5,829,437 and 6,061,589. These employ a scan plate that is placed on the surface of the breast of a patient lying on her back. To demonstrate feasibility, a microwave, wide band of 1 to 10 GHz, confocal, pulsed microwave breast cancer 3-D imaging system has been developed that successfully images tumors in 3-D in human breast tissues that were not otherwise detectable in mammograms. For these human tests, the patient lies on her back with a microwave transparent dielectric material lightly positioned on her breast. A small, hand-held antenna, positioned in known locations, both illuminates the breast and collects the backscatter at each location. Data from all of the locations is then digitally processed to form a 3-D image. This system, while satisfactory for preliminary tests, requires substantial examination times and would need substantial training of the attending technician to hold the scan plate steady and to precisely define the antenna positions with respect to the anatomy of the patient.
The technical foundation behind this device has been disclosed under the following US patents and are hereby incorporated by reference: Non Invasive System for Breast Cancer Detection, U.S. Pat. No. 5,704,355 (Jan. 6, 1998), J. E. Bridges; Breast Cancer Detection, Imaging and Screening by Electromagnetic Millimeter Waves U.S. Pat. No. 5,807,257 (Sep. 15, 1998), J. E. Bridges; Microwave Method and System to Detect and Located Cancers in Heterogeneous Tissues, U.S. Pat. No. 5,829,437 (Nov. 3, 1998), J. E. Bridges; Microwave Antennas for Cancer Detection System, U.S. Pat. No. 6,061,589 (May 9, 2000), Jack E. Bridges, et. al; Microwave Antennas for Cancer Detection System, U.S. Pat. No. 6,061,589 (May 9, 2000), Jack E. Bridges, et. al; and Microwave Discrimination Between Malignant and Benign Breast Tumors, U.S. Pat. No. 6,421,558 (Jul. 16, 2002), Jack E. Bridges, et al.
The aforementioned microwave systems require improvements for routine screening, such as by technicians or for clinical, or diagnostic use by the physicians. A number of novel features, heretofore not available are needed and are provided by the present invention.